The Multimedia Message Service (MMS) provides for the transmission of graphics, video clips, sound files and text messages over wireless networks. Mobile network operators (MNO) and wireless service providers typically implement MMS using MMS Centers (MMSCs), which implement store-and-forward delivery of multimedia messages from providers of multimedia content to mobile subscribers, as well as multimedia message exchange between mobile subscribers. Once a multimedia message is received the MMSC will identify one or more intended recipients of the multimedia message, locate the receiving device of a recipient, which may be a cellular telephone, a PDA or handheld computer, transcode the multimedia message as required for playback on the recipient's device according to the device's multimedia capabilities, and send the multimedia message to the recipient's device.
One challenge facing MNOs and wireless service providers involves adapting multimedia content for the wide variety of mobile subscriber devices in use. Adapting content currently incurs a relatively large computational expense when transcoding content for different playback environments. This is especially acute with respect to multimedia messages sent between disparate mobile subscriber devices. For example, when content that was previously transcoded for playback on one mobile subscriber device is sent from the mobile subscriber device to another mobile subscriber device, the transcoded content is typically transcoded again by the MMSC for playback on the intended recipient's device. This typically results in a lower playback quality than would be the case if the original content was transcoded for playback on the intended recipient's device. In order for the content to be sent from the mobile subscriber device to another mobile subscriber device of a different type, the transcoded data is typically transcoded again to suit the receiving device, often resulting in a further reduction in quality. Adapting content is further hampered by the complexity of implementing Digital Rights Management (DRM) techniques to control access to content by mobile subscriber devices with different DRM capabilities at a time when DRM standards for MMS are still emerging. Techniques which efficiently adapt multimedia content in these respects would therefore be advantageous.
Furthermore, with current systems, in order to provide control over content each mobile subscriber needs to connect to a content server and download the content in a “pull” mode. A system that would allow mobile subscribers to send content to each other that appears to the recipient as if the content were received in a “push” mode, and that allows for rights management for multimedia devices with different DRM capabilities would also be advantageous.